This invention relates to optical devices and networks.
Future networks for broadband communications will need higher bandwidths for data transmission. One avenue to obtaining higher bandwidth entails using wavelength division multiplexed (WDM) optical networks. A WDM optical network can simultaneously transmit several optical signals in a single optical fiber. The simultaneously transmitted optical signals have different wavelengths, and WDM receivers selectively accept signals based on their wavelength.
Some optical networks are also dynamically reconfigurable so that transmission routes can be rapidly changed. Dynamic reconfigurability can be achieved using programmable optical add/drop multiplexers (OADM""s) and optical cross connects (OXC""s). OADM""s add optical signals to and drop optical signals from trunk optical fibers. OXC""s switch optical signals between different trunk fibers. Contemporary OXC""s and OADM""s can switch optical signals transparently. OXC""s and OADM""s using thermal control signals can transparently switch routes of optical signal at frequencies of about 2 kilo Hertz (Khz).
Herein, a transparent process is defined to be a process that changes a property or routing of an optical signal without an intermediate conversion of the optical signal into an electrical signal.
Other features and advantages of the invention will be apparent from the following description and claims.
In one aspect, the invention features a method of producing a wavelength shift into an optical signal. The method includes transparently producing a coherent temporal array of signals (CTAS) from the incoming optical signal and broadening the signals of the CTAS to produce an interference pattern by transmitting the CTAS through a dispersive medium. The method also includes selectively transmitting a peak of the interference pattern to an output terminal. A wavelength of a center of the transmitted peak has a selected wavelength shift with respect to a wavelength of the incoming optical signal.
In a second aspect, the invention features a method of producing a wavelength shift into an optical signal. The method includes transparently producing a coherent temporal array of signals (CTAS) from the incoming optical signal and broadening the signals of the CTAS to produce an interference pattern by transmitting the incoming optical signal through a dispersive medium. The method also includes selectively transmitting a peak of the interference pattern to an output terminal. A wavelength of a center of the transmitted peak has a selected wavelength shift with respect to a wavelength of the incoming optical signal.
In a third aspect, the invention features a method of switching optical signals in an optical network. The method includes receiving an optical signal from a first optical conduit of the network and transparently shifting a wavelength of the received optical signal. The method also includes transmitting the optical signal with the shifted wavelength to a second optical conduit of the network.
In a fourth aspect, the invention features an apparatus for routing optical pulses. The apparatus includes a variable temporal splitter (VTS) and a dispersive medium connected serially to the VTS. The VTS is capable of transparently producing a coherent temporal array of pulses (CTAP) from a received optical pulse. The dispersive medium is capable of broadening the pulses of the CTAP to form an interference pattern with a plurality of peaks. The apparatus includes a 1xc3x97M wavelength division multiplexer (WDM) coupled to receive one of the peaks.
In a fifth aspect, the invention features an optical switch. The optical switch includes a variable wavelength shifter (VWS) and a wavelength division multiplexer (WDM) coupled to receive optical pulses with shifted wavelengths from the VWS. The VWS transparently shifts a wavelength of a received optical pulse.
Various embodiments provide transparent optical multiplexers and switches with switching frequencies of between a few tens of giga Hertz to a few hundreds of giga Hertz. The optical switches can provide high speed programmable OXC and OADM""s for use in reconfigurable optical networks.